1. Field of the Invention
This invention pertains to the art of radar detection and more specifically to a radar detection system and technique for detecting a target immersed in clutter utilizing the polarization of a signal reflected from the target.
2. Description of the Prior Art
It is well known in the art that a polarized signal incident upon clutter will become depolarized on reflection. Prior art techniques have considered the use of polarization information to enhance target detection and clutter discrimination. In U.S. Pat. No. 3,772,689, a method is disclosed in which the amplitude maxima and minima of the reflected signal are noted as the polarization of the incident signal is varied. The amount of polarization variation for a maximum ratio of echo amplitudes is representative of the complexity of the illuminated target. Such a system, while utilizing polarization information does not develop a sufficient detection statistic nor does it minimize the effects of clutter. Thus a method is sought with which the polarization information contained in a reflected radar signal may be completely characterized.
Polarization of signals received by a radar system may be utilized to describe the polarization characteristics, known as Stokes parameters. In the past, Stokes parameters have been used to describe the polarization of optical frequency signals. A description of such use is presented by Born & Wolf, "Principles of Optics", McMillan Company, 1964, (pages 30-32 and 544-545). The present invention provides an apparatus which utilizes the Stokes parameters of a returned radar signal to enhance the detection of a radar target immersed in clutter.